Method for connecting structural sandwich plate members with channel-shaped connecting members

ABSTRACT

To connect two structural sandwich plate members ( 10, 20 ), each is provided with a channel-shaped connecting member ( 14, 24 ) fitted between and projecting from the outer plates ( 11, 12, 21, 22 ). The two plate members ( 10, 20 ) are abutted and welds ( 31, 32 ) formed between the outer plates ( 11, 12, 21, 22 ).

The present invention relates to methods for connecting structuralsandwich plate members which comprise two outer plates and a core ofplastics or polymer material bonded to the outer plates with sufficientstrength to substantially contribute to the structural strength of themember.

Structural sandwich plate members are described in U.S. Pat. No.5,778,813 and U.S. Pat. No. 6,050,208, which documents are herebyincorporated by reference, and comprise outer metal, e.g. steel, platesbonded together with an intermediate elastomer core, e.g. of unfoamedpolyurethane. These sandwich plate systems may be used in many forms ofconstruction to replace stiffened steel plates and greatly simplify theresultant structures, improving strength and structural performance(stiffness, damping characteristics) while saving weight. Furtherdevelopments of these structural sandwich plate members are described inInternational Patent Application WO 01/32414, also incorporated herebyby reference. As described therein, foam forms may be incorporated inthe core layer to reduce weight and transverse metal sheer plates may beadded to improve stiffness.

According to the teachings of WO 01/32414 the foam forms can be eitherhollow or solid. Hollow forms generate a greater weight reduction andare therefore advantageous. The forms described in that document are notconfined to being made of lightweight foam material and can also be makeof other materials such as wood or steel boxes.

International Patent Application WO 02/078948 is a further developmentof the concept of including hollow forms and describes forms that areeasy to manufacture and assemble, in particular hollow elongate formsmade from snap-together pieces are described.

To connect together two (or more) structural sandwich plate members,rolled or extruded members such as described in InternationalApplication PCT/GB02/00157 may be used. These members accommodate a widevariety of forms of join but each different arrangement of plate membersrequires a different joining member. British Patent Application GB-2 380970-A describes a universal connector in the form of a solid bar ofoctagonal cross-section which is welded into the periphery of astructural sandwich plate member with part of the bar projecting outfrom between the faceplates of the structural sandwich plate member. Two(or more) plates with such connectors can be welded together in variousdifferent ways. This connector solves the problem of requiring manydifferent members to join plate members in many different arrangementsbut is relatively heavy.

It is an aim of the present invention to provide a method of connectingstructural sandwich plate members that uses a single, lightweightconnector to connect plate members together.

According to the present invention, there is provided a method ofconnecting two structural sandwich plate members each of which comprisestwo outer plates and a core of plastics or polymer material bonded tothe outer plates with sufficient strength to transfer shear forcestherebetween, the method comprising:

providing in the edges of the structural sandwich plate members to bejoined channel-shaped connecting members, the connecting members fittingbetween, and projecting beyond the ends of the outer plates of theirrespective structural sandwich plate members;

placing the structural sandwich plate members together so that the edgesto be joined abutt, or nearly abutt; and

forming a weld between the outer plates of the two structural sandwichplate members.

The connecting member is preferably channel-shaped. The convex side ofthe connecting member projects from between the two outer plates. Whenthe plate members abutt, the connecting member spaces apart the outerplates of the two plate members to allow a full thickness weld to beformed and acts as backing bar for that weld.

The invention also provides a structural sandwich plate membercomprising:

two outer plates;

a core of plastics or polymer material bonded to the outer plates withsufficient strength to substantially contribute to the structuralstrength of the member; and

at least one connecting member fitted between, and projecting beyond theends of said outer plates.

The materials, dimensions and general properties of the outer plates ofthe structural sandwich plate member of the invention may be chosen asdesired for the particular use to which the structural sandwich platemember is to be put and in general may be as described in U.S. Pat. No.5,778,813 and U.S. Pat. No. 6,050,208. Steel or stainless steel iscommonly used in thicknesses of 0.5 to 20 mm and aluminium may be usedwhere light weight is desirable. Similarly, the plastics or polymer coremay be any suitable material, for example an elastomer such aspolyurethane, as described in U.S. Pat. No. 5,778,813 and U.S. Pat. No.6,050,208.

Lightweight forms may be included in the core, as described in WO01/32414 and WO 02/078948. It should be noted that the lightweight formsserve to reduce the mass of the structural sandwich plate member andneed not contribute significantly to its structural strength. Theprincipal requirements on the lightweight forms are that they are oflower density than the plastics or polymer material forming the core andhave sufficient thermal and mechanical properties to maintain thedesired shape during injection and curing of the plastics or polymercore. The layout of the forms within the core may be as described inBritish Patent Application GB-2 389 072-A filed 29 May 2002.

The present invention will be described below with reference to anexemplary embodiment and the accompanying schematic drawings, in which:

FIG. 1 is a cross-sectional view of parts of two structural sandwichplate members joined according to a first method of the presentinvention; and

FIG. 2 is an enlarged part cross-sectional view of a structural sandwichplate member according to the present invention.

In the various drawings, like parts are indicated by like referencenumerals.

Each of the structural sandwich plate members 10, 20 shown in FIG. 1comprises upper and lower outer plates (faceplates) 11, 12, 21, 22 whichmay be of steel and have a thickness of e.g. in the range of from 0.5 to20 mm. Edge plates are welded between the faceplates 11, 12, 21, 22around their outer peripheries to form a closed cavity. In the cavitybetween the faceplates 11, 12, 21, 22 is a core 13, 23 of compact (i.e.unfoamed) plastics or polymer material, preferably a polyurethaneelastomer. This core may have a thickness in the range of from 15 to 200mm. The core 13, 23 is bonded to the faceplates 11, 12, 21, 22 withsufficient strength and has sufficient mechanical properties to transfershear forces expected in use between the two faceplates. The bondstrength between the core 13, 23 and faceplates 11, 12, 21, 22 should begreater than 3MPa, preferably 6MPa, and the modulus of elasticity of thecore material should be greater than 250 MPa. For low load applications,such as floor panels, where the typical use and occupancy loads are ofthe order of 1.4 kPa to 7.2 kPa, the bond strength may be lower, e.g.approximately 1 MPa. By virtue of the core layer, the structuralsandwich plate member has a strength and load bearing capacity of astiffened steel plate having a substantially greater plate thickness andsignificant additional stiffening.

To reduce the weight of the structural sandwich plate member 10, anarray of lightweight forms may be provided, occupying a substantial partof the internal volume of the plate member. The lightweight forms do notneed to significantly contribute to the structural strength of the plateand they require only to have thermal and mechanical propertiessufficient to withstand the pressure of injection of the material toform core 13 and the heat from the exothermic reaction of the coreduring curing.

Along an edge at which one of the structural sandwich plate members isto be joined to another plate member of like type, the edge member takesthe form of a channel section 14, 24 fitting between the faceplates 11,12, 21, 22 with its concave side facing inward. The base portions 14 a,24 a and corner portions 14 b, 14 c, 24 b, 24 c project outwardly of theends 11 a, 12 a, 21 a, 22 a of the faceplates of the two structuralsandwich plate members such that when two plate members are buttedagainst each other, spaces are formed between the ends of the platemembers 11 a, 21 a and 12 a, 22 a and bounded by the corner portions 14b, 24 b and 14 c, 24 c. To join the two structural sandwich platemembers 10, 20, a weld 31, 32 is formed in each of the spaces. A directconnection between the faceplates is thereby achieved quickly andsimply. The corner portions 14 b, c and 24 b, c act as weld preparationfor this weld.

FIG. 2 shows the position of the connecting member 14 in structuralsandwich plate member 10 in more detail. As there shown, the connectingmember 14 projects so that the tangents A-A, B-B to the corners 14 b, 14c pass through the ends 11 a, 12 a of the faceplates 11, 12. Thisensures that sufficient space is left between the faceplates of adjacentplate members to form a substantial weld whilst the corner portions 14b, 14 c form weld preparations for the weld to join the faceplates. Theradius of curvature, r, of the corner portions 14 b, 14 c is preferablyequal to twice the thickness, t, of the metal plate from which theconnecting member 14 is rolled. The thickness, t, will depend on theapplication to which the plates are to be put but will in general becomparable to the thickness of the faceplates 11, 12, e.g. 5 or 6 mm forshipbuilding applications.

The connecting member, if connected to the faceplates with sufficientstrength, can contribute significantly to the strength of the platemember in the region of the join. This ensures that the plate member hassufficient strength even if the heat from the weld between thefaceplates damages the elastomer core. In this case the connectingmember can be welded to the faceplates with one pass seal welds 33.

If, in the final structure the connecting pieces 14, 24 do not need tocarry loads between the structural sandwich plate members, they can bebonded to their respective plate members by the cores 13, 23. Thus, whenthe plate members are made, the connectors 14, 24 can be held in placeby any simple convenient method, appropriate to the method ofconstruction of the panels. For example, if the plate members are madein a mold, the clamping force of the mold bearing on the faceplates maybe sufficient to hold the connecting members in place. Alternatively, alight adhesive, or a few spot welds may suffice. If the plate member ismade using the faceplates to define the cavity for injection of thecore, without a mold, the connecting members may be held in place with ashipbuilding adhesive or with light welds.

Manufacture of the plate members may be performed in situ, or off-sitein factory conditions and the finished panel transported to theinstallation site.

It will be appreciated that the above description is not intended to belimiting and that other modifications and variations that fall withinthe scope of the present invention, which is defined by the appendedclaims, are possible.

1. A method of connecting two structural sandwich plate members each ofwhich comprises two outer plates and a core of plastics or polymermaterial bonded to the outer plates with sufficient strength to transfershear forces therebetween, the method comprising: providing in the edgesof the structural sandwich plate members to be joined channel-shapedconnecting members, the connecting members fitting between, andprojecting beyond the ends of the outer plates of their respectivestructural sandwich plate members; placing the structural sandwich platemembers together so that the edges to be joined abutt, or nearly abutt;and forming a weld between the outer plates of the two structuralsandwich plate members.
 2. A method according to claim 1 wherein saidconnecting members are channel-shaped.
 3. A method according to claim 2wherein in said step of providing, said connecting members arepositioned so that the tangents to the corner thereof pass through theends of said outer plates.
 4. A method according to claim 1, 2 or 3wherein in said step of providing, said connecting members are welded tosaid outer plates by a one-pass seal weld.
 5. A method according toclaim 1, 2 or 3 wherein the step of providing connecting members isperformed at a different site than the steps of placing the structuralsandwich plate members together and forming a weld.
 6. A structuralsandwich plate member comprising: two outer plates; a core of compactplastics or polymer material bonded to the outer plates with sufficientstrength to substantially contribute to the structural strength of themember; and at least one connecting member fitted between, andprojecting beyond the ends of said outer plates. said connecting memberhaving surfaces adapted to be welded to a like connecting member in alike structural sandwich plate member.
 7. A structural sandwich platemember according to claim 6 wherein said connecting member ischannel-shaped.
 8. A structural sandwich plate member according to claim7 wherein tangents to the corners of said connecting members passthrough the ends of said outer plates.
 9. A structural sandwich platemember according to claim 6, 7 or 8 wherein the radius of curvature ofthe corners of said connecting member is at least twice the thickness ofsaid connecting member.
 10. A structural sandwich plate member accordingto claim 6, 7 or 8 wherein said connecting member is fixed to said outerplates by one-pass seal welds.
 11. A structural sandwich plate memberaccording to claim 6, 7, or 8 wherein said connecting member is formedfrom rolled metal.
 12. A method according to claim 4 wherein the step ofproviding connecting members is performed at a different site than thesteps of placing the structural sandwich plate members together andforming a weld.
 13. A structural sandwich plate member according toclaim 9 wherein said connecting member is fixed to said outer plates byone-pass seal welds.
 14. A structural sandwich plate member according toclaim 9 wherein said connecting member is formed from rolled metal. 15.A structural sandwich plate member according to claim 10 wherein saidconnecting member is formed from rolled metal.